Trapped vortex fuel injector and method for manufacture

ABSTRACT

A trapped vortex fuel injector includes a main body having an annular portion and a semi-annular portion coaxially aligned with the annular portion. The semi-annular portion extends downstream from the annular portion. An inner wall and an opposing outer wall of the main body extend between the annular and semi-annular portions. The annular portion at least partially defines a combustion air flow passage through the trapped vortex fuel injector. The semi-annular portion defines a trapped vortex pre-mix zone downstream from the combustion air flow passage. The main body further defines a fuel circuit that is fully circumscribed within the main body and that extends between the annular portion and the semi-annular portion. A plurality of fuel injection ports provide for fluid communication between the fuel circuit and the trapped vortex pre-mix zone. The main body may be fabricated using an additive manufacturing process.

FIELD OF THE INVENTION

The present invention generally involves a fuel injector for acombustor. More specifically, the invention relates to a trapped vortexfuel injector incorporated into a system for injecting a combustiblemixture into a combustion gas flow field downstream from a primarycombustion zone defined within the combustor and a method formanufacturing the trapped vortex fuel injector.

BACKGROUND OF THE INVENTION

A gas turbine generally includes a compressor section, a combustionsection having a combustor and a turbine section. The compressor sectionprogressively increases the pressure of the working fluid to supply acompressed working fluid to the combustion section. The compressedworking fluid is routed through and/or around a fuel nozzle that extendsaxially within the combustor. A fuel is injected into the flow of thecompressed working fluid to form a combustible mixture. The combustiblemixture is burned within a combustion zone to generate combustion gaseshaving a high temperature, pressure and velocity. The combustion gasesflow through one or more liners or ducts that define a hot gas path intothe turbine section. The combustion gases expand as they flow throughthe turbine section to produce work. For example, expansion of thecombustion gases in the turbine section may rotate a shaft connected toa generator to produce electricity.

The temperature of the combustion gases directly influences thethermodynamic efficiency, design margins, and resulting emissions of thecombustor. For example, higher combustion gas temperatures generallyimprove the thermodynamic efficiency of the combustor. However, highercombustion gas temperatures may increase the disassociation rate ofdiatomic nitrogen, thereby increasing the production of undesirableemissions such as oxides of nitrogen (NO_(x)) for a particular residencetime in the combustor. Conversely, a lower combustion gas temperatureassociated with reduced fuel flow and/or part load operation (turndown)generally reduces the chemical reaction rates of the combustion gases,thereby increasing the production of carbon monoxide (CO) and unburnedhydrocarbons (UHCs) for the same residence time in the combustor.

In order to balance overall emissions performance while optimizingthermal efficiency of the combustor, certain combustor designs includemultiple fuel injectors that are arranged around the liner andpositioned generally downstream from the primary combustion zone. Thefuel injectors generally extend radially through the liner to providefor fluid communication into the combustion gas flow field. This type ofsystem is commonly known in the art and/or the gas turbine industry asLate Lean Injection (LLI) and/or as axial fuel staging.

In operation, a portion of the compressed working fluid is routedthrough and/or around each of the fuel injectors and into the combustiongas flow field. A liquid or gaseous fuel from the fuel injectors isinjected into the flow of the compressed working fluid to provide a leanor air-rich combustible mixture which spontaneously combusts as it mixeswith the hot combustion gases, thereby increasing the firing temperatureof the combustor without producing a corresponding increase in theresidence time of the combustion gases inside the combustion zone. As aresult, the overall thermodynamic efficiency of the combustor may beincreased without sacrificing overall emissions performance.

One challenge with injecting a fuel into the combustion gas flow fieldusing existing LLI or axial fuel staging systems is that the momentum ofthe combustion gases generally inhibits adequate radial penetration ofthe liquid fuel into the combustion gas flow field. As a result, localevaporation of the liquid fuel may occur along an inner wall of theliner at or near the fuel injection point, thereby potentially resultingin a high temperature zone and/or high thermal stresses. In addition,achieving and sustaining combustion in a gas turbine combustor isdifficult due to various factors such as but not limited to fuelcontent, fuel temperature, ambient air conditions, engine load and/oroperating condition of the gas turbine. These various factors maypotentially create flow instabilities which may affect the NOx emissionslevels generated by the combustor.

Current solutions to address these issues include extending at least aportion of the fuel injector radially inward through the liner and intothe combustion gas flow field. However, this approach exposes the fuelinjectors to the hot combustion gases which may potentially impact themechanical life of the component and may lead to fuel coke buildup.Therefore, an improved system for injecting a combustible mixture intothe combustion gas flow field including a trapped vortex fuel injectordisposed downstream from a primary combustion zone and method forfabricating the trapped vortex fuel injector would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

One embodiment of the present invention is a trapped vortex fuelinjector. The trapped vortex fuel injector includes a main body havingan annular portion and a semi-annular portion that is coaxially alignedwith the annular portion. The semi-annular portion extends downstreamfrom the annular portion. An inner wall and an opposing outer wallextend between the annular and semi-annular portions. The annularportion at least partially defines a compressed or combustion air flowpassage through the main body. The semi-annular portion defines atrapped vortex pre-mix zone that is downstream from the combustion airflow passage. The main body further defines a fuel circuit that is fullycircumscribed within the main body and that extends between the annularportion and the semi-annular portion. A plurality of fuel injectionports provide for fluid communication between the fuel circuit and thetrapped vortex pre-mix zone.

Another embodiment of the present invention is a system for injecting acombustible mixture into a combustion gas flow field downstream from aprimary combustion zone of a combustor. The system includes a liner thatdefines a combustion gas flow path downstream from a primary fuel nozzleand/or primary combustion zone. The liner includes an inner side and anouter side and an injector opening that extends through the liner. Thesystem further includes a trapped vortex fuel injector that is disposeddownstream from the primary fuel nozzle. The trapped vortex fuelinjector includes a main body that extends through the injector opening.The main body includes an annular portion that extends outwardly fromthe outer side of the liner, and a semi-annular portion that iscoaxially aligned with the annular portion. The semi-annular portionextends downstream from the annular portion inwardly from the inner sideof the liner. The main body also includes an inner wall and an opposingouter wall that extend between the annular and semi-annular portions.The annular portion defines a compressed or combustion air flow passage.The semi-annular portion defines a trapped vortex pre-mix zone that isdownstream from the combustion air flow passage. The main body furtherdefines a fuel circuit that is in fluid communication with a fuelsupply. The fuel circuit is fully circumscribed within the main body andextends between the annular portion and the semi-annular portion. Themain body also defines a plurality of fuel injection ports that providefor fluid communication between the fuel circuit and the trapped vortexpre-mix zone.

The present invention also includes a gas turbine. The gas turbineincludes a compressor, a combustor disposed downstream from thecompressor and a turbine that is disposed downstream from the combustor.The combustor includes a primary fuel nozzle, a liner that extendsdownstream from the primary fuel nozzle where the liner at leastpartially defines a combustion gas flow path within the combustor. Theliner has an inner side and an outer side. The gas turbine also includesa trapped vortex fuel injector that is disposed downstream from theprimary fuel nozzle. The trapped vortex fuel injector comprises a mainbody that extends through the liner. The main body includes an annularportion that extends outwardly from the outer side of the line and asemi-annular portion that is coaxially aligned with the annular portion.The semi-annular portion extends downstream from the annular portioninwardly from the inner side of the liner into the combustion gas flowpath. The annular portion defines a compressed or combustion air flowpassage within the main body. The semi-annular portion defines a trappedvortex pre-mix zone that is downstream from the combustion air flowpassage. The main body further defines a fuel circuit that is in fluidcommunication with a fuel supply. The fuel circuit is fullycircumscribed within the main body and extends between the annularportion and the semi-annular portion. The main body further defines aplurality of fuel injection ports in fluid communication with the fuelcircuit. The fuel injection ports provide for fluid communicationbetween the fuel circuit and the trapped vortex pre-mix zone.

Another embodiment of the current invention includes a method forfabricating a main body of a trapped vortex fuel injector where the mainbody defines a fuel circuit that is fully circumscribed within the mainbody and that extends between an annular portion and a semi-annularportion of the main body. The main body further defines a plurality offuel injection ports that provide for fluid communication between thefuel circuit and a trapped vortex pre-mix zone. The method comprises thesteps of determining three-dimensional information of the main bodyincluding the fuel circuit, converting the three-dimensional informationinto a plurality of slices that define a cross-sectional layer of themain body where at least some of the plurality of slices defines a voidthat is representative of the fuel circuit within the cross-sectionallayer, and successively forming each layer of the main body by fusing ametallic powder using laser energy.

One embodiment of the present invention includes a trapped vortex fuelinjector having a main body where the main body includes an annularportion, a semi-annular portion coaxially aligned with the annularportion and extending downstream from the annular portion and an innerwall and an opposing outer wall that extend between the annular andsemi-annular portions. The annular portion defines a combustion air flowpassage. The semi-annular portion defines a trapped vortex pre-mix zonethat is downstream from the combustion air flow passage. The main bodyfurther defines a fuel circuit that is fully circumscribed within themain body and that extends between the annular portion and thesemi-annular portion. The main body also defines a plurality of fuelinjection ports that provide for fluid communication between the fuelcircuit and the trapped vortex pre-mix zone. The main body is formed byan additive manufacturing process. The additive manufacturing processcomprises determining three-dimensional information of the main bodyincluding the fuel circuit, converting the three-dimensional informationinto a plurality of slices that define a cross-sectional layer of themain body where at least some of the plurality of slices defines a voidwithin the cross-sectional layer representing a portion of the fuelcircuit, and successively forming each layer of the main body by fusinga metallic powder using laser energy.

Those of ordinary skill in the art will better appreciate the featuresand aspects of such embodiments, and others, upon review of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a functional block diagram of an exemplary gas turbine withinthe scope of the present invention;

FIG. 2 is a cross-section side view of a portion of an exemplary cantype combustor as may be incorporate various embodiments of the presentinvention;

FIG. 3 is a cross sectional side view of a trapped vortex fuel injectorincluding a portion of the combustor as shown in FIG. 2, according toone embodiment of the present invention;

FIG. 4 is a cross sectional bottom view of the trapped vortex fuelinjector as shown in FIG. 3, according to various embodiments of thepresent invention;

FIG. 5 is a cross sectional side view of the trapped vortex fuelinjector as shown in FIG. 3, according to one embodiment of the presentinvention;

FIG. 6 is a partial cross sectional perspective view of a portion of thetrapped vortex fuel injector as shown in FIG. 3, according to variousembodiments of the present invention;

FIG. 7 is a partial cross sectional perspective view of a portion of thetrapped vortex fuel injector as shown in FIG. 3, according to variousembodiments of the present invention;

FIG. 8 is a cross sectional view representative of either an exemplaryfuel circuit or an exemplary cooling channel of the trapped vortex fuelinjector as shown in FIGS. 3 and 5, according to one or more embodimentsof the present invention; and

FIG. 9 is a flow chart illustrating an exemplary embodiment of a methodfor fabricating a main body portion of a fuel injector as shown invarious embodiments in FIGS. 2-8.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components. The terms“upstream” and “downstream” refer to the relative direction with respectto fluid flow in a fluid pathway. For example, “upstream” refers to thedirection from which the fluid flows, and “downstream” refers to thedirection to which the fluid flows. The term “radially” refers to therelative direction that is substantially perpendicular to an axialcenterline of a particular component, and the term “axially” refers tothe relative direction that is substantially parallel to an axialcenterline of a particular component.

Each example is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope or spirit thereof.For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents. Although exemplary embodiments of thepresent invention will be described generally in the context of atrapped vortex fuel injector and system for injecting a combustiblemixture into a combustion gas flow field downstream within a combustorincorporated into a gas turbine for purposes of illustration, one ofordinary skill in the art will readily appreciate that embodiments ofthe present invention may be applied to any combustor incorporated intoany turbomachine and is not limited to a gas turbine combustor unlessspecifically recited in the claims.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 provides a functional blockdiagram of an exemplary gas turbine 10 that may incorporate variousembodiments of the present invention. As shown, the gas turbine 10generally includes an inlet section 12 that may include a series offilters, cooling coils, moisture separators, and/or other devices topurify and otherwise condition a working fluid (e.g., air) 14 enteringthe gas turbine 10. The working fluid 14 flows to a compressor sectionwhere a compressor 16 progressively imparts kinetic energy to theworking fluid 14 to produce a compressed working fluid 18.

The compressed working fluid 18 is mixed with a fuel 20 from a fuelsupply system 22 to form a combustible mixture within one or morecombustors 24. The combustible mixture is burned to produce combustiongases 26 having a high temperature, pressure and velocity. Thecombustion gases 26 flow through a turbine 28 of a turbine section toproduce work. For example, the turbine 28 may be connected to a shaft 30so that rotation of the turbine 28 drives the compressor 16 to producethe compressed working fluid 18. Alternately or in addition, the shaft30 may connect the turbine 28 to a generator 32 for producingelectricity. Exhaust gases 34 from the turbine 28 flow through anexhaust section 36 that connects the turbine 28 to an exhaust stack 38downstream from the turbine 28. The exhaust section 36 may include, forexample, a heat recovery steam generator (not shown) for cleaning andextracting additional heat from the exhaust gases 34 prior to release tothe environment.

The combustor 24 may be any type of combustor known in the art, and thepresent invention is not limited to any particular combustor designunless specifically recited in the claims. For example, the combustor 24may be a can type or a can-annular type of combustor. FIG. 2 provides across-section side view of a portion of an exemplary gas turbine 10including a portion of the compressor 16 and an exemplary can typecombustor 24. As shown in FIG. 2, an outer casing 40 surrounds at leasta portion of the combustor 24. An end cover 42 is coupled to the outercasing 40 at one end of the combustor 24. The end cover 42 and the outercasing 40 generally define a high pressure plenum 44. The high pressureplenum 44 receives the compressed working fluid 18 from the compressor16.

At least one primary fuel nozzle 46 extends axially downstream from theend cover 42 within the outer casing 40. A liner 48 extends downstreamfrom the primary fuel nozzle 46 within the outer casing 40. The liner 48is generally annular and extends at least partially through the highpressure plenum 44 so as to at least partially define a combustion gasflow path 50 within the combustor 24 for routing the combustion gases 26through the high pressure plenum 44 towards the turbine 28 (FIG. 1).

The liner 48 may be a singular liner or may be divided into separatecomponents. For example, as illustrated in FIG. 2, the liner 48 maycomprise of a combustion liner 52 that is disposed proximate to theprimary fuel nozzle 46 and a transition duct 54 that extends downstreamfrom the combustion liner 52. The liner 48 and/or the transition duct 54may be shaped so as to accelerate the flow of the combustion gases 26through the combustion gas flow path 50 upstream from a stage ofstationary nozzles (not shown) that are disposed proximate to an inletof the turbine 28 within the combustion gas flow path 50. A primarycombustion zone 56 is defined downstream from the primary fuel nozzle46. The primary combustion zone 56 may be at least partially defined bythe liner 48. As shown, the combustion gases 26 define or form acombustion gas flow field 58 within the combustion gas flow path 50downstream from the primary combustion zone 56 during operation of thecombustor 24.

The liner 48 generally includes an inner wall 60, an opposing outer wall62 and an injector opening 64 that extends through the inner wall 60 andthe outer wall 62. The injector opening 64 provides for fluidcommunication through the liner 48. As shown, the liner 48 may includemultiple injector openings 64 that are arranged around the liner 48downstream from the primary fuel nozzle 46 and/or the primary combustionzone 56.

As previously stated, achieving and sustaining combustion in a gasturbine combustor is difficult due to various factors such as but notlimited to fuel content, fuel temperature, ambient air conditions,engine load and/or operating condition of the gas turbine. These variousfactors may create flow instabilities which may affect the NOx emissionslevels generated by the combustor. In order to overcome the flowinstabilities, the present invention includes at least one trappedvortex fuel injector 100 that provides for fluid communication throughthe liner 48 and into the combustion gas flow field 58 downstream fromthe primary combustion zone 56. The injector 100 may provide for fluidcommunication through the liner 48 at any point that is downstream fromthe primary fuel nozzle 46 and/or the primary combustion zone 56.

FIG. 3 provides a cross sectional side view of the trapped vortex fuelinjector 100 including a portion of the liner 48 as shown in FIG. 2,according to one embodiment of the present invention. As shown in FIG.3, the trapped vortex fuel injector 100 includes a main body 102. Themain body 102 may be made as a single piece during manufacturing. Forexample, the main body 102 made be manufacture using one or moreadditive manufacturing processes. Thus, the main body 102 has amonolithic construction, and is different from a component that has beenmade from a plurality of component pieces that have been joined togethervia brazing, welding or other joining process to form a singlecomponent.

In one embodiment, the main body 102 includes an annular portion 104 anda semi-annular portion 106 that extends from the annular portion 104along a centerline 108 of the fuel injector 102. The annular portion104, when installed in the combustor 24, is partially disposed at leastpartially within the injector opening 64 defined within the liner 48.The annular portion 104 extends along the centerline 108 outwardly fromthe outer wall of the liner 48, thus substantially positioning theannular portion 104 outside of the combustion gas flow field 58. Forexample, the annular portion 104 may terminate at and/or adjacent to theinner wall 60 of the liner 48.

The semi-annular portion 106 terminates at an end wall 110 defined bythe main body 102. The semi-annular portion 106 is coaxially alignedwith the annular portion 104 along the centerline 108. When extendingthrough the liner 48, the semi-annular portion 106 extends from theannular portion 104 inwardly from the inner wall of the liner 48, thuspositioning at least a portion the semi-annular portion 106, includingthe end wall 110 within the combustion gas flow path 50 (FIG. 2) and/orinto the combustion gas flow field 58.

The main body 102 includes an inner wall or side 112 and an opposingouter wall or side 114. The inner and outer walls 112, 114 extendbetween the annular and semi-annular portions 104, 106. The inner wall112 at least partially defines a compressed or combustion air flowpassage 116 through the annular portion 104 of the main body 102. Aninlet 118 is defined at an upstream end of the combustion air passage116 and/or the main body 102. The inlet 118 provides for fluidcommunication into the combustion air flow passage 116. In particularembodiments, the semi-annular portion 106 is generally oriented so thatthe outer wall 114 faces towards or into the flow field 58 of thecombustion gases 26 from the primary combustion zone 56. In oneembodiment, the inlet 118 is in fluid communication with the highpressure plenum 44 (FIG. 2) and/or another compressed air source forproviding the compressed working fluid 18 to the combustion air flowpassage 116. In one embodiment, as shown in FIG. 3, a plurality ofswirler vanes 120 extend within the combustion air flow passage 116. Theswirler vanes 120 may be configured or angled to provide angular swirlto the compressed working fluid 18 about the centerline 108 as it flowsthrough the combustion air flow passage 116.

In various embodiments, as shown in FIG. 3, the semi-annular portion 106at least partially defines a trapped vortex pre-mix zone 122 downstreamfrom the combustion air flow passage 118. In operation, the semi-annularportion 106 defines a bluff body or obstruction within the combustiongas flow field 58. As the combustion gases 26 flow past the semi-annularportion 106, a low pressure, recirculation or vertical flow zone iscreated downstream from the inner wall 112 of the semi-annular portion106, thereby causing the combustion gases to spin or swirl in a vorticalflow motion. As a result, the semi-annular portion 106 provides ordefines the trapped vortex pre-mix zone 122 adjacent to or near theinner wall 112. The trapped vortex pre-mix zone 122 extends along atleast a portion of the inner wall 112 of the semi-annular portion 106 ofthe main body 102.

In one embodiment, as shown in FIG. 3, the main body 102 defines atleast one fuel circuit 124. The fuel circuit 124 is fully circumscribedwithin the main body 102 between the inner wall 112 and the outer wall114. In various embodiments, the fuel circuit 122 is formed via one ormore additive manufacturing methods, techniques or processes, thusproviding for greater accuracy and/or more intricate details within thefuel circuit 124 than previously producible by conventionalmanufacturing processes. As shown in FIG. 3, the fuel circuit 124extends between the annular portion 104 and the semi-annular portion106.

The fuel circuit 124 is in fluid communication with a fuel source suchas the fuel supply 22 (FIG. 2). As shown in FIG. 3, the fuel source mayprovide a liquid and/or a gas fuel 20 to the fuel circuit 124. In oneembodiment, the fuel circuit 124 is in fluid communication with a fuelplenum 126 that is at least partially defined by the main body 102. Inone embodiment, the fuel plenum 126 may be defined proximate to theinlet 118 of the combustion air flow passage 116. The fuel plenum 126may be fluidly connected to the fuel source such as the fuel supply 22.

In various embodiments, the main body 102 defines at least one fuelinjection port 128 that is in fluid communication with the fuel circuit124. The fuel injection port 128 is disposed downstream from the fuelsource and/or the fuel plenum 126.

FIG. 4 provides a cross sectional bottom view of the trapped vortex fuelinjector 100 according to various embodiments of the present invention.In particular embodiments, as show in FIGS. 3 and 4, the main body 102at least partially defines a plurality of fuel injection ports 128. Thefuel injection ports 128 are defined within the semi-annular portion 106of the main body 102. In one embodiment, as shown in FIG. 3, the fuelinjection ports 128 are defined along the inner wall 112, thus providingfor fluid communication from the fuel circuit 124 through the inner wall112 and into the trapped vortex pre-mix zone 122.

As shown in FIG. 4, the fuel injection ports 128 may becircumferentially spaced within the semi-annular portion 106 to providefor fluid communication through the inner wall 112 and into the trappedvortex pre-mix zone 122. In one embodiment, at least a portion of thefuel injection ports 128 are oriented to induce swirl to a flow of thefuel 20 as it flows from the fuel circuit 124 into the trapped vortexpre-mix zone 122. For example, at least some of the fuel injection ports128 may be angled with respect to the centerline 108.

In operation, a portion of the compressed working fluid 18 flows throughthe inlet 118 and into the combustion air flow passage 116 into thetrapped vortex recirculation zone 122. Fuel 20 is injected through thefuel injection ports 128 into the trapped vortex recirculation zone 122thus forming a pre-mixed combustible mixture 130 therein. The vorticalflow of the combustion gases 26 enhance mixing and/or combustion of thecombustible mixture, thus increasing overall flame stability within thecombustor and reducing or enhancing NOx emissions levels.

The temperature differential between the fuel supplied to the fuelcircuit 124 and the combustion gases results in a cooling effect to themain body 102 of the trapped vortex fuel injector 100, thus allowing adeeper penetration of the semi-annular portion 106 of the main body 102than conventional late lean or axially staged fuel injectors, thusfurther enhancing the benefits of axial staged fuel injection. However,in particular combustors, the cooling effect provided by the fuel onlyis insufficient to meet life requirements. As a result, the trappedvortex fuel injector 100 may further include at least one coolingchannel 132.

FIG. 5 is a cross sectional side view of the trapped vortex fuelinjector 100 including a portion of the liner 48 as shown in FIG. 3,according to one embodiment of the present invention. In one embodiment,as shown in FIG. 5, the main body 102 also defines at least one coolingchannel 132. The cooling channel 132 is fully circumscribed within themain body 102 between the inner wall 112 and the outer wall 114. Invarious embodiments, the cooling channel 132 is formed via one or moreadditive manufacturing methods, techniques or processes, thus providingfor greater accuracy and/or more intricate details within the coolingchannel 132 than previously producible by conventional manufacturingprocesses.

As shown in FIG. 3, the cooling channel 132 extends between the annularportion 104 and the semi-annular portion 106. In particular embodiments,a cooling air inlet 134 is defined within the annular portion 104 of themain body 102. The cooling air inlet 134 is in fluid communication withthe cooling channel 132. In particular embodiments, the cooling airinlet 134 provides for fluid communication between a compressed airsupply such as the high pressure plenum 44 (FIG. 2) and the coolingchannel 132. In various embodiments, the cooling air inlet 134 ispositioned outside of the liner 48 and/or outside of the combustion gasflow path 50 or the combustion gas flow field 58.

In particular embodiments, the main body 102 defines at least onecooling air outlet 136 that is in fluid communication with the coolingchannel 132 downstream from the cooling air inlet 134. In particularembodiments, the main body 102 defines a plurality of the cooling airoutlets 136. In various embodiments, at least a portion of the coolingair outlets 136 are defined within the semi-annular portion 106 of themain body 102. In one embodiment, as shown in FIGS. 4 and 5, the coolingair outlet 136 is disposed or defined on the end wall 110, thusproviding for fluid communication from the cooling channel through theend wall 110. In one embodiment, at least one of the cooling air outlets136 is disposed or defined on the outer wall 114 along the semi-annularportion 106, thus providing for fluid communication from the coolingchannel through the outer wall 114, thereby providing at least one ofconvection or film cooling to the outer wall 114.

In particular embodiments, as shown in FIGS. 4 and 5, a plurality ofcooling air outlets 136 is disposed or defined on the inner wall 112along the semi-annular portion 106, thus providing for fluidcommunication from the cooling channel through the inner wall 112 intothe trapped vortex pre-mix zone 122. In particular embodiments, the mainbody 102 defines a plurality of the cooling air outlets 136 where atleast a portion of the cooling air outlets provide for fluidcommunication through the inner wall 112 and at least one of the outerwall 114 and the end wall 110.

In one embodiment, as shown in FIG. 4, one or more of the cooling airoutlets 136 are oriented to direct a jet of the compressed working fluid18 into a jet of the fuel 20 flowing from at least one of the fuelinjection ports 128, thus enhancing the pre-mixing of the fuel andcompressed working fluid 18 within the trapped vortex pre-mix zone 122prior to injection into the combustion gas flow field 58. In particularembodiments, at least one of the cooling air outlets 136 are oriented toinduce swirl to the jet or flow of the compressed working fluid 18flowing from the corresponding cooling channel 136 into the trappedvortex pre-mix zone, thus enhancing the pre-mixing of the fuel andcompressed working fluid 18 within the trapped vortex pre-mix zone 122prior to injection into the combustion gas flow field 58.

In one embodiment, at least one cooling channel 136 may extend from theannular portion 104 of the main body 102 into the semi-annular portion106 and back into the annular portion 104. The cooling air outlet 136 isdefined along the annular portion 104. As a result, the compressedworking fluid 18 may be routed through the main body 102 for cooling andthen routed back into the high pressure plenum 44 and/or routed towardsa head end of the combustor 24 were it may be used for pre-mixing withfuel 20 from the axially extending fuel nozzle 46 and/or for cooling ofother combustor components.

FIGS. 6 and 7 provide partial cross sectional perspective views of aportion of the main body 102 according to various embodiments of thepresent invention. In one embodiment, as shown in FIG. 6, at least oneof the fuel circuit 124 and/or the cooling channel 132 extend in ahelical pattern 138 within the semi-annular portion 106. In thisembodiment, the cooling air outlet 136 or outlets 136 and/or the fuelinjector ports 128 may be disposed along the inner wall 112. In oneembodiment, as shown in FIG. 7, at least one of the fuel circuit 124and/or the cooling channel 132 extend in a generally serpentine orwinding pattern 140 within the semi-annular portion 106. In thisembodiment, the cooling air outlet 136 or outlets 136 and/or the fuelinjector ports 128 may be disposed along the inner wall 112.

FIG. 8 is a cross sectional view representative of either an exemplaryfuel circuit 124 or an exemplary cooling channel 132, according to oneor more embodiments of the present invention. In particular embodiments,as shown in FIG. 8, one or more flow features 142 may be defined withinthe fuel circuit 124 and/or the cooling channel 132. The flow feature orfeatures 142 may include concave of convex dimples 144, ribs 146, slots148, grooves 150 or other features for enhancing cooling effectivenessof the fuel 20 and/or the compressed working fluid 18. In variousembodiments, the flow feature 136 or features are formed via one or moreadditive manufacturing methods, techniques or processes previouslydiscussed, thus providing for greater accuracy and/or more intricatedetails within the cooling channel 132 than previously producible byconventional manufacturing processes.

In operation, a portion of the compressed working fluid 18 is routedinto the cooling channel 132 via the cooling air inlet 134. Thecompressed working fluid 18 flows through the cooling channel 132, thusremoving thermal energy from the semi-annular portion 106 by providingat least one of convection, impingement and/or conduction cooling to theinner, outer and/or the end walls 112, 114 and 110 respectively, of thesemi-annular portion 106. In particular embodiments, the compressedworking fluid 18 flows across the flow features 142 to enhance thecooling effectiveness of the compressed working fluid 18, therebyfurther enhancing the mechanical life of the fuel injector 102. Inaddition or in the alternative, the fuel 20 may flow across the flowfeatures 142 to enhance the cooling effectiveness of the fuel 20 and toraise the temperature of the fuel 20, thereby further enhancing themechanical life of the fuel injector 102 and/or increasing flamestability within the combustion gas path 50.

Conventional LLI fuel injectors are generally expensive to fabricateand/or repair because the conventional LLI fuel injector designs includecomplex assemblies and joining of a large number of components. Morespecifically, the use of braze joints can increase the time needed tofabricate such components and can also complicate the fabricationprocess for any of several reasons, including: the need for an adequateregion to allow for braze alloy placement; the need for minimizingunwanted braze alloy flow; the need for an acceptable inspectiontechnique to verify braze quality; and, the necessity of having severalbraze alloys available in order to prevent the re-melting of previousbraze joints. Moreover, numerous braze joints may result in severalbraze runs, which may weaken the parent material of the component. Thepresence of numerous braze joints can undesirably increase the weightand manufacturing cost of the component.

In order to reduce costs, weight and to provide the fuel circuit 124,the cooling channel 132 and/or the flow feature 142 as described, themain body 102 can be made using an additive manufacturing process. Inone embodiment, the additive manufacturing process of Direct Metal LaserSintering (DMLS) is a preferred method of manufacturing the main body102 described herein.

FIG. 9 is a flow chart illustrating an exemplary embodiment of a method200 for fabricating the main body 102 as described herein and as shownin FIGS. 2-8. Method 200 includes fabricating at least the main body 102of the trapped vortex fuel injector 100 using the Direct Metal LaserSintering (DMLS) process.

DMLS is a known manufacturing process that fabricates metal componentsusing three-dimensional information, for example a three-dimensionalcomputer model of the component. The three-dimensional information isconverted into a plurality of slices where each slice defines a crosssection of the component for a predetermined height of the slice. Thecomponent is then “built-up” slice by slice, or layer by layer, untilfinished. Each layer of the component is formed by fusing a metallicpowder using a laser.

Accordingly, method 200 includes the step 202 of determiningthree-dimensional information of the main body 102 and the step 204 ofconverting the three-dimensional information into a plurality of sliceswhere each slice defines a cross-sectional layer of the main body 102.Each slice may further define a void that is representative of a portionof at least one of the fuel circuit 124, the cooling channel 132 and/orthe flow feature 142. The main body 102 is then fabricated using DMLS,or more specifically each layer is successively formed 206 by fusing ametallic powder using laser energy. Each layer has a size between about0.0005 inches and about 0.001 inches. As a result, the fuel circuit 124may be defined fully circumscribed within the main body 102. In additionor in the alternative, the cooling channel 132 and/or the flow feature142 may also be formed in this manner. Additive manufacturing allows forthe fuel circuit 124, the cooling channel 132, and/or the flow features142 to be formed in intricate previously non-producible and/or costprohibitive patterns and/or shapes.

The main body 102 may be fabricated using any suitable laser sinteringmachine. Examples of suitable laser sintering machines include, but arenot limited to, an EOSINT® M 270 DMLS machine, a PHENIX PM250 machine,and/or an EOSINT® M 250 Xtended DMLS machine, available from EOS ofNorth America, Inc. of Novi, Mich. The metallic powder used to fabricatethe main body 104 is preferably a powder including cobalt chromium, butmay be any other suitable metallic powder, such as, but not limited to,HS 1888 and INCO625. The metallic powder can have a particle size ofbetween about 10 microns and 74 microns, preferably between about 15microns and about 30 microns.

Although the methods of manufacturing the main body 102 including thefuel circuit 124, cooling channel 132 and/or cooling channels 132 and/orthe flow features 142 have been described herein using DMLS as thepreferred method, those skilled in the art of manufacturing willrecognize that any other suitable rapid manufacturing methods usinglayer-by-layer construction or additive fabrication can also be used.These alternative rapid manufacturing methods include, but not limitedto, Selective Laser Sintering (SLS), 3D printing, such as by inkjets andlaserjets, Sterolithography (SLS), Direct Selective Laser Sintering(DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM),Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing(LNSM) and Direct Metal Deposition (DMD).

The various embodiments described herein and illustrated in FIGS. 2-9,provide various technical advantages over existing production systemsfor injecting fuel into a combustion gas flow field. For example,conventional fuel injectors or “late lean” fuel injectors, depend on theproper fuel/air momentum leaving the fuel injector to penetrate into thecross flow or combustion gas flow field for optimal emissions andhardware durability. The fuel circuits enable the semi annular portionof the main body to protrude into the combustion gas flow field and toact as a trapped vortex feature. For example, fuel flowing through thefuel circuits provides cooling to the semi-annular portion of the mainbody, thus extending the life of the fuel injector while providing theadded benefit of more complete mixing within the trapped vortex pre-mixzone. Further cooling may be realized by providing the cooling channels,thus further enhancing the life of the trapped vortex fuel injector andallowing for deep penetration of the fuel-air mixture into thecombustion gas flow field. As a result, the fuel injectors presentedherein are not as sensitive to the engine load as current productionaxial staged or late lean fuel injectors.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A trapped vortex fuel injector, comprising: amain body having an annular portion, a semi-annular portion coaxiallyaligned with the annular portion, the semi-annular portion extendingdownstream from the annular portion, an inner wall and an opposing outerwall that extend between the annular and semi-annular portions, whereinthe annular portion defines a combustion air flow passage and thesemi-annular portion defines a trapped vortex pre-mix zone downstreamfrom the combustion air flow passage; wherein the main body furtherdefines a fuel circuit fully circumscribed within the main body andextending between the annular portion and the semi-annular portion, anda plurality of fuel injection ports; and wherein the fuel injectionports provide for fluid communication between the fuel circuit and thetrapped vortex pre-mix zone.
 2. The trapped vortex fuel injector as inclaim 1, wherein the main body defines a fuel plenum proximate to theupstream end, wherein the fuel circuit is in fluid communication withthe fuel plenum.
 3. The trapped vortex fuel injector as in claim 1,wherein the plurality of fuel injection ports is circumferentiallyspaced within the semi-annular portion and provide for fluidcommunication through the inner wall.
 4. The trapped vortex fuelinjector as in claim 1, wherein the fuel circuit comprises one or moreflow features defined by the main body along the fuel circuit.
 5. Thetrapped vortex fuel injector as in claim 1, wherein at least a portionof the fuel circuit extends partially within the main body in at leastone of a serpentine pattern and a helical pattern.
 6. The trapped vortexfuel injector as in claim 1, wherein at least a portion of the fuelinjection ports are oriented to induce swirl to a flow of fuel as itflows from the fuel circuit into the trapped vortex pre-mix zone.
 7. Thetrapped vortex fuel injector as in claim 1, wherein the main bodyfurther defines: a cooling channel fully circumscribed within the mainbody and extending between the annular portion and the semi-annularportion; a cooling air inlet defined within the annular portion, thecooling air inlet being in fluid communication with the cooling channel;and a plurality of cooling air outlets in fluid communication with thecooling channel downstream from the cooling air inlet.
 8. The trappedvortex fuel injector as in claim 7, wherein at least one of the coolingair outlets provides for fluid communication through the inner wall intothe trapped vortex pre-mix zone.
 9. The trapped vortex fuel injector asin claim 7, wherein at least one of the cooling air outlets is orientedto direct a jet of cooling air into a jet of fuel flowing from at leastone of the fuel injection ports.
 10. The trapped vortex fuel injector asin claim 7, wherein at least a portion of the cooling air outlets areoriented to induce swirl to a flow of cooling air flowing from thecooling channel into the trapped vortex pre-mix zone.
 11. The trappedvortex fuel injector as in claim 7, wherein the cooling air outletsprovide for fluid communication through at least one of the inner wall,the outer wall and an end wall of the semi-annular portion.
 12. A systemfor injecting a combustible mixture into a combustion gas flow fielddownstream from a primary combustion zone of a combustor, comprising; aliner that defines a combustion gas flow path downstream from a primaryfuel nozzle, the liner having an inner side, an opposing outer side andan injector opening that extends through the liner; a trapped vortexfuel injector disposed downstream from the primary fuel nozzle, thetrapped vortex fuel injector having a main body that extends through theinjector opening, the main body including an annular portion thatextends outwardly from the outer side, a semi-annular portion coaxiallyaligned with the annular portion, the semi-annular portion extendingdownstream from the annular portion inwardly from the inner side, aninner wall and an opposing outer wall that extend between the annularand semi-annular portions, wherein the annular portion defines acombustion air flow passage and the semi-annular portion defines atrapped vortex pre-mix zone downstream from the combustion air flowpassage; wherein the main body defines a fuel circuit in fluidcommunication with a fuel supply, the fuel circuit fully circumscribedwithin the main body and extending between the annular portion and thesemi-annular portion, the main body further defining a plurality of fuelinjection ports; and wherein the fuel injection ports provide for fluidcommunication between the fuel circuit and the trapped vortex pre-mixzone.
 13. The system as in claim 12, wherein the plurality of fuelinjection ports is circumferentially spaced within the semi-annularportion and provide for fluid communication from the fuel circuitthrough the inner wall.
 14. The system as in claim 12, wherein the fuelcircuit comprises one or more flow features defined by the main bodyalong the fuel circuit.
 15. The system as in claim 12, wherein at leasta portion of the fuel injection ports are oriented to induce swirl to aflow of fuel as it flows from the fuel circuit into the trapped vortexpre-mix zone.
 16. The system as in claim 12, wherein the main bodyfurther defines: a cooling channel fully circumscribed within the mainbody and extending between the annular portion and the semi-annularportion; a cooling air inlet defined within the annular portion, thecooling air inlet being in fluid communication with the cooling channel;a plurality of cooling air outlets in fluid communication with thecooling channel downstream from the cooling air inlet, at least one ofthe cooling air outlets providing for fluid communication through theinner wall into the trapped vortex pre-mix zone; and wherein at leastone of the cooling air outlets is oriented to direct a jet of coolingair into a jet of fuel flowing from at least one of the fuel injectionports.
 17. A gas turbine, comprising: a compressor; a combustor disposeddownstream from the compressor; a turbine disposed downstream from thecombustor; and wherein the combustor comprises: a primary fuel nozzle; aliner that extends downstream from the primary fuel nozzle, the linerdefining a combustion gas flow path within the combustor, the linerhaving an inner side and an outer side; a trapped vortex fuel injectordisposed downstream from the primary fuel nozzle, the trapped vortexfuel injector having a main body that extends through the liner, themain body including an annular portion that extends outwardly from theouter side, a semi-annular portion coaxially aligned with the annularportion, the semi-annular portion extending downstream from the annularportion inwardly from the inner side into the combustion gas flow path,wherein the annular portion defines a combustion air flow passage andthe semi-annular portion defines a trapped vortex pre-mix zonedownstream from the combustion air flow passage; wherein the main bodydefines a fuel circuit in fluid communication with a fuel supply, thefuel circuit fully circumscribed within the main body and extendingbetween the annular portion and the semi-annular portion, the main bodyfurther defining a plurality of fuel injection ports in fluidcommunication with the fuel circuit; and wherein the fuel injectionports provide for fluid communication between the fuel circuit and thetrapped vortex pre-mix zone.
 18. The gas turbine as in claim 17, whereinthe plurality of fuel injection ports is circumferentially spaced withinthe semi-annular, wherein at least a portion of the fuel injection portsare oriented to induce swirl to a flow of fuel as it flows from the fuelcircuit into the trapped vortex pre-mix zone.
 19. The gas turbine as inclaim 17, wherein the fuel circuit comprises one or more flow featuresdefined by the main body along the fuel circuit.
 20. The gas turbine asin claim 17, wherein the main body further defines: a cooling channelfully circumscribed within the main body and extending between theannular portion and the semi-annular portion; a cooling air inletdefined within the annular portion, the cooling air inlet being in fluidcommunication with the cooling channel; a plurality of cooling airoutlets in fluid communication with the cooling channel downstream fromthe cooling air inlet, at least one of the cooling air outlets providingfor fluid communication into the trapped vortex pre-mix zone.
 21. Atrapped vortex fuel injector, comprising: a main body having an annularportion, a semi-annular portion coaxially aligned with the annularportion, the semi-annular portion extending downstream from the annularportion, an inner wall and an opposing outer wall that extend betweenthe annular and semi-annular portions, wherein the annular portiondefines a combustion air flow passage and the semi-annular portiondefines a trapped vortex pre-mix zone downstream from the combustion airflow passage; wherein the main body further defines a fuel circuit fullycircumscribed within the main body and extending between the annularportion and the semi-annular portion, and a plurality of fuel injectionports; wherein the fuel injection ports provide for fluid communicationbetween the fuel circuit and the trapped vortex pre-mix zone; andwherein the main body is formed by an additive manufacturing process,the additive manufacturing process comprising: determiningthree-dimensional information of the main body including the fuelcircuit; converting the three-dimensional information into a pluralityof slices that define a cross-sectional layer of the main body, whereinat least some of the plurality of slices defines a void within thecross-sectional layer representing a portion of the fuel circuit; andsuccessively forming each layer of the main body by fusing a metallicpowder using laser energy or electron beam.
 22. The trapped vortex fuelinjector as in claim 21, wherein the additive manufacturing process is alaser sintering process.
 23. The trapped vortex fuel injector as inclaim 21, wherein the additive manufacturing process is a direct metallaser sintering (DMLS) process.
 24. The trapped vortex fuel injector asin claim 21, wherein the main body defines a fuel plenum proximate tothe upstream end, wherein the fuel circuit is in fluid communicationwith the fuel plenum.
 25. The trapped vortex fuel injector as in claim21, wherein the plurality of fuel injection ports is circumferentiallyspaced within the semi-annular portion and provide for fluidcommunication through the inner wall.
 26. The trapped vortex fuelinjector as in claim 21, wherein the fuel circuit comprises one or moreflow features defined by the main body along the fuel circuit.
 27. Thetrapped vortex fuel injector as in claim 21, wherein at least a portionof the fuel circuit extends partially within the main body in at leastone of a serpentine pattern and a helical pattern.
 28. The trappedvortex fuel injector as in claim 21, wherein at least a portion of thefuel injection ports are oriented to induce swirl to a flow of fuel asit flows from the fuel circuit into the trapped vortex pre-mix zone. 29.The trapped vortex fuel injector as in claim 21, wherein the main bodyfurther defines: a cooling channel fully circumscribed within the mainbody and extending between the annular portion and the semi-annularportion; a cooling air inlet defined within the annular portion, thecooling air inlet being in fluid communication with the cooling channel;and a plurality of cooling air outlets in fluid communication with thecooling channel downstream from the cooling air inlet.
 30. The trappedvortex fuel injector as in claim 29, wherein at least one of the coolingair outlets provides for fluid communication through the inner wall intothe trapped vortex pre-mix zone.
 31. The trapped vortex fuel injector asin claim 29, wherein at least one of the cooling air outlets is orientedto direct a jet of cooling air into a jet of fuel flowing from at leastone of the fuel injection ports.
 32. The trapped vortex fuel injector asin claim 29, wherein at least a portion of the cooling air outlets areoriented to induce swirl to a flow of cooling air flowing from thecooling channel into the trapped vortex pre-mix zone.